Multi-functional micro electromechanical devices and method of bulk manufacturing same

ABSTRACT

A method of bulk manufacturing SiC sensors is disclosed and claimed. Materials other than SiC may be used as the substrate material. Sensors requiring that the SiC substrate be pierced are also disclosed and claimed. A process flow reversal is employed whereby the metallization is applied first before the recesses are etched into or through the wafer. Aluminum is deposited on the entire planar surface of the metallization. Photoresist is spun onto the substantially planar surface of the Aluminum which is subsequently masked (and developed and removed). Unwanted Aluminum is etched with aqueous TMAH and subsequently the metallization is dry etched. Photoresist is spun onto the still substantially planar surface of Aluminum and oxide and then masked (and developed and removed) leaving the unimidized photoresist behind. Next, ITO is applied over the still substantially planar surface of Aluminum, oxide and unimidized photoresist. Unimidized and exposed photoresist and ITO directly above it are removed with Acetone. Next, deep reactive ion etching attacks exposed oxide not protected by ITO. Finally, hot phosphoric acid removes the Al and ITO enabling wires to connect with the metallization. The back side of the SiC wafer may be also be etched.

ORIGIN OF THE INVENTION

The invention described herein was made by an employee of the UnitedStates Government, and may be manufactured and used by the governmentfor government purposes without the payment of any royalties therein andtherefor.

FIELD OF THE INVENTION

This invention is in the field of micro electromechanical devices orrelated materials.

BACKGROUND OF THE INVENTION

Strain gages have been bonded on metal diaphragms to produce pressuresensors or accelerometers. Because these transducers are made ofmaterials with dissimilar properties, they suffer from coefficient ofthermal expansion (CTE) mismatch, which leads to fatigue and earlyfailure. In addition the production process is time consuming since eachstrain gage must be placed on the diaphragm one at a time.

I am a named inventor of U.S. Pat. No. 5,637,905 to Carr et al. and itdiscloses a high temperature pressure and displacement microsensor madefrom a Si substrate. A first coil structure is positioned within arecess in the Si and a pressure diaphragm is glass bonded about theperiphery to the rim of the semiconductor substrate. A second coilstructure is positioned on the underside of the pressure diaphragm andis electrically isolated from the first coil structure. The coils areinductively coupled together and provide an output indicative of changesin the coupling between the coils.

My U.S. Pat. No. 6,248,646 discloses a process for making an array ofSiC wafers on standard larger industry sized wafers. This patentdiscusses the operating conditions for SiC and SiC-On-Insulatortechnology and cites the need for sensors made from SiC.

U.S. Pat. No. 5,447,067 to Biebl et al. discloses an acceleration sensorconstructed on Silicon-On-Insulator substrate. Piezoresistors aredisclosed for use in conjunction with a proof mass suspended by one ormore resilient elements. These sensors are not useable in harshenvironments. U.S. Pat. No. 5,576,250 to Diem et al. discloses a processfor the production of accelerometers using Silicon-On-Insulatortechnology. The '250 patent discloses an accelerometer with movingelements consisting of one or more flexible beams supporting a seismicmass. Further, the '250 patent discloses packaging of accelerometers andthe driving circuit by multichip module technology.

Sensors manufactured from 3C-SiC, 4H-SiC and 6H-SiC are used in harshenvironments, for example high temperature environments, high vibrationenvironments, radiation environments and corrosive environments. “H”means hexagonal and “C” as used in “3C” means Cubic and both refer tothe crystalline structure of SiC.

SiC is a wide band gap semiconductor. Semiconductors are materials whoseelectrical conductivity is between that of a conductor and that of aninsulator. “If an electron in an atom happens to be in an energy levelwhich overlaps a higher, empty level, that electron proves to beessentially free from its original atom. It is then capable of movingfreely through the solid, and the material will be a conductor, i.e., ametal. However, if the electron in the highest energy state of the atomexists in a level which does not overlap higher energy levels, thiselectron will be firmly held to its atom. Such a material will be anonconductor of electricity. An intermediate case exists if the energylevels do not overlap but are close enough so that the energy gapbetween them is of the order of thermal energies. These materials arecalled semiconductors.” Introduction To Physics For Scientists AndEngineers, Copyright 1969, McGraw-Hill, Inc., Library of CongressCatalog Card Number 69-13598, ISBN 07-008833-0, pgs. 804-805.

The semiconductor SiC is known as a wide band gap semiconductor meaningthat electrons in the valence band must traverse an energy gap ofseveral electron Volts (eV) at 300 K to reach the conduction band. SiCis operable at temperatures up to 873 K without substantial leakagecurrent. Leakage current, for example that is due to the temperature ofthe operating environment, is kept to a minimum in SiC.

Batch fabrication of a single function type SiC sensors, namely,pressure sensors, has been demonstrated and has piqued the interest ofmany who desire stable sensors operable in harsh environments. SiC is,however, a very expensive material with wafer costs much greater thanconventional silicon semiconductor for a two inch diameter wafer. Onesuch wafer can produce between 100-400 pressure sensors.

There is not enough demand, however, for batch production of pressuresensors alone. Unlike silicon based sensors, silicon carbide sensorshave a low volume specialized market The current process for fabricatingsilicon carbide sensors is limited to producing only one type of sensorper wafer at a time and, as such, the commercial viability of siliconcarbide is greatly reduced. Further, there is no known process forsimultaneously making different devices (sensors) having differentfunctionality at the same time. Several different types of sensors existsuch as accelerometers having proof masses suspended therein andpressure sensors having diaphragms.

There is a need for SiC accelerometers having suspended proof masses.Presently, such devices are not manufactured and are not believed toexist. Further, there is a need for the batch fabrication ofmultifunctional, multistructural sensors and other devices manufacturedfrom SiC.

Although batch fabrication of SiC pressure sensors has beendemonstrated, the economic viability of SiC sensors heretofore has beenin doubt because there is no need for the mass production of one type ofsensor, i.e, a pressure sensor. Industry remains reluctant to devote itsresources to commercial production of SiC sensors for the followingreasons:

(1) unlike Si sensors, SiC sensors of any one particular type have a lowvolume, specialized market;

(2) SiC has an inherently high material and capital cost when only onesensor is made in bulk from a single wafer and as a result theprofitability incentive does not exist to encourage commercialproduction; and,

(3) the current process for fabricating these devices is limited toproducing only one type of device at a time therefore doubling thefabrication cost for making two different devices.

One major problem in the batch manufacturing of SiC multistructuralsensors is that some of the sensors such as accelerometers require theconstruction of apertures or annular recesses in the substrate. Anaperture or a recess is three dimensional. Sensors such asaccelerometers desirably include a suspended mass in the substrate fromwhich they are manufactured. This mass is made from SiC and thepiezoresistance of the n-type or p-type SiC which connects the mass tothe remainder of the substrate is measured. Mathematical analysis of thepiezoresistance determines the value and direction of acceleration. Thesuspension of the mass requires that the substrate be etched veryprecisely.

It is not possible to precisely construct the apertures or annularrecesses in the SiC substrate before metallization because theyinterfere adversely with the remaining fabrication/manufacture of theSiC sensor. SiC sensors precisely measure the piezoresistance ofspecific areas of n-type SiC and, therefore, it is necessary that thecontact metallization be precisely located and engage the n-type SiC inthose specific areas. Positioning of the contact metallization iscontrolled by a masking process where photoresist is spun onto the waferthat is held under suction on a chuck. Therefore, if the wafer wasperforated prior to application of the photoresist it would not bepossible to create a suction due to the perforations. Further, thesuction from the chuck through the perforations in the wafer woulddisturb the uniform application of the photoresist. SiC wafers arerotated between 1000 to 7000 revolutions per minute as photoresist isapplied to the center of the wafer. As photoresist is spread radially itwill impact whatever three dimensional apertures or recesses exist andwill not spread evenly in those areas thereby resulting in low yield ofthe wafer. By low yield, it is meant that many sensors will be defectivedue to poor patterning of the photoresist. At costs approaching $3,500for a two inch diameter SiC wafer with epilayer, it is important thatits use be maximized. It is desired that approximately 100-400 sensorsbe generated from each wafer so as to maximize the economy of volume andbatch production of the sensors.

A better understanding of the invention will be had when reference ismade to the SUMMARY OF THE INVENTION, BRIEF DESCRIPTION OF THE DRAWINGS,DESCRIPTION OF THE INVENTION and CLAIMS which follow hereinbelow.

SUMMARY OF THE INVENTION

The simultaneous fabrication of multi-functional SiC microelectromechanical devices is disclosed, claimed and described herein.Simultaneous fabrication of flow sensors, pressure sensors,accelerometers, inertial sensors, angular rate sensors and yaw ratesensors from SiC is accomplished by this invention. These sensors may beconfigured as desired by the particular user for the user's specificapplication. The instant invention allows for the simultaneousproduction of SiC sensors of different types from the same wafer thusgreatly increasing the viability of SiC for use as sensors.

Substrates comprising other materials are specifically contemplated bythis invention. AlN, BC, BN, and Al₂O₃ may, for example be used. Anysubstrate upon which an epilayer may be grown is contemplated to bewithin the scope of this invention.

This invention offers a global platform for bulk micro machining processin SiC or in any one of several other material mentioned above. Itoffers various manufacturers the opportunity to simultaneously producemultifunctional products on a single SiC wafer (or wafer made fromanother material) and thereby greatly lower capital equipment andproduction cost.

The sensing principle utilizes the piezoresistance of the single crystalSiC or other material. Piezoresistance indicates a dependence ofresistivity on mechanical strain. In particular, the instant inventionby way of example utilizes the piezoresistance of the n- or p-typeepilayer of a SiC wafer. The low resistivity n-type epilayer, in effect,acts as a variable resistor which is mounted atop a high resistivityp-type SiC substrate. It is the mechanical deformation of this n-typeepilayer which causes resistivity changes which are measured by applyinga voltage differential across a portion of the n- (or, p-) typeepilayer. As the resistance changes as a function of mechanicaldeformation of the n-type epilayer, the flow of electrical currentthrough the n-type epilayer will change for a given voltage. The instantinvention discloses a novel SiC sensor as well as a method for bulkmanufacturing of multifunction SiC sensors. The examples given for thebulk manufacturing of SiC sensors are equally applicable to sensors madefrom the other materials mentioned above.

One major factor in bulk micromachined SiC sensors is the presence ofthree dimensional structures. It is difficult to apply a planar coatingof photoresist if three dimensional apertures or recesses exist in thesubstrate. To overcome this barrier, this invention employs a processflow reversal whereby contact metal is first sputter deposited onto then-type epilayer of the SiC wafer before recesses or apertures are etchedinto or through the wafer. Additionally, if and once holes are piercedthrough the wafer it is extremely difficult to hold the wafer in avacuum chuck. Aluminum is deposited by electron beam evaporation (e-beamevaporation) onto the entire planar surface of the contact metal.Photoresist is spun on the substantially planar contact metal and thenmasked and exposed under ultraviolet light. Photoresist imidized undersuch exposure is stripped away with developer and then the unwantedAluminum is etched with TMAH (Trimethyl Ammonium Hydroxide). Next, themetal(s) (in this case layers of Platinum, Tantalum Disilicide andTitanium) is/are dry etched using the Aluminum as the etch mask.

Next, photoresist is spun onto the remaining Aluminum and the oxidelayer on the n-type epilayer. Another mask is applied, exposed underultraviolet light and the imidized photoresist is stripped away afterdeveloping and the unimidized photoresist is left behind. Next IndiumTin Oxide (ITO or Nickel (Ni)) is sputter deposited on the Aluminum andthe unimidized photoresist. The ITO, however, does not completely coverthe unimidized photoresist enabling Acetone to dissolve the unimidizedphotoresist when submersed in Acetone. This process lifts off ITO (orNickel) on the photoresist. Now with the oxide exposed and the remainderof the wafer protected by the ITO (or Nickel), deep reactive ion etchingoccurs and recesses or apertures may be formed in the SiC substrate.This process may be used to produce a suspended proof mass in the SiCwafer. The proof mass may move out of the plane in which it resides atrest. Recesses in any shape or form may be created in the SiC waferusing these techniques. The ITO and the remaining Aluminum is removedwith hot phosphoric acid. Wires can then be attached to the contactmetal such as Platinum. Other metals may be used for the contactDepending on the configuration of the sensor desired, the back side ofthe SiC wafer may be etched to provide a diaphragm.

Accordingly, it is an object of the present invention to provide anaccelerometer made from SiC, for example, or from any material used as asubstrate upon which an epilayer may be grown or deposited. It is afurther object of the present invention to provide a method of producingan accelerometer made from SiC. Further, it is a further object of thepresent invention to provide a method of simultaneously making aplurality of multifunctional sensors from SiC, for example, or from anymaterial used as a substrate upon which an epilayer may be grown ordeposited. It is a further object of the present invention tomanufacture a plurality of similar or diverse sensors simultaneously bya process which includes the step of first applying contact metal toengage the SiC and to sense resistance changes of the SiC in response tomechanical deformation of the SiC. It is a further object of the presentinvention to provide SiC sensors capable of operating in harshenvironments.

These and other objects will be best understood when reference is madeto the BRIEF DESCRIPTION OF THE DRAWINGS, DESCRIPTION OF THE INVENTION,AND CLAIMS which follow hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art schematic illustration of ultraviolet lightapplied to a mask which is positioned in proximity to the back side of aportion (p-type) of a 3C-SiC, 4H-SiC or 6H-SiC wafer having an n-typeepilayer on the front side thereof.

FIG. 2 is a prior art schematic illustration of the portion of the waferillustrated in FIG. 1 with the imidized photoresist removed and with alayer of Indium Tin Oxide, or Nickel, deposited on the p-type portion ofthe back side of the wafer.

FIG. 3 is a prior art schematic illustration of the photoresistillustrated in FIG. 2 removed by immersing the wafer in Acetone, so asto lift off the ITO (or Nickel) cap.

FIG. 4 is a prior art schematic illustration of deep reactive ionetching using Sulfur HexaFluoride (SF₆) to physically and chemicallyetch the back side of the portion of the SiC wafer forming a cavity insuch a diaphragm.

FIG. 5 is a prior art schematic illustrating the removal of the ITO fromthe SiC in a Hydrochloric Acid (HCl) solution.

FIG. 6 is a prior art schematic illustration of a pressure sensor formedin the SiC which has a cavity and n-type SiC piezoresistive sensors.

FIG. 6A is a prior art schematic illustration of the pressure sensorillustrated in FIG. 6 shown with pressure applied thereto.

FIG. 7 is a front side view of the pressure sensor of FIGS. 6 and 6A

FIG. 8 is a macroscopic view of an entire one inch SiC waferschematically illustrating a grid system where sensors will bemanufactured.

FIGS. 9-13 illustrate preparation of the n-type epilayer formetallization wherein:

FIG. 9 is a schematic illustration of the application of growing ordepositing oxide (or Silicon Nitride or other dielectric) followed byapplication of photoresist to the n-type epilayer of SiC which is thenfollowed by the application of masked ultraviolet light.

FIG. 10 is a schematic illustration similar to FIG. 9 with the imidizedphotoresist being first removed by developer and not shown.

FIG. 11 is a schematic illustration similar to FIG. 10 with the oxidebeing etched by buffered hydrofluoric acid (BHF).

FIG. 12 is a schematic illustration similar to FIG. 11 after etching ofoxide.

FIG. 13 is a schematic illustration similar to FIG. 12 after submersionin Acetone which removed the unimidized photoresist.

FIG. 14 is a schematic illustration of a portion of a SiC wafer with aPlatinum/Tantalum Disilicide/Titanium (Pt/TaSi₂/Ti) trimetal appliedthereto.

FIG. 15 is an enlargement of a portion of FIG. 15 illustrating thematerial of the ohmic contact.

FIG. 16 is a schematic illustration of the SiC wafer portion of FIG. 14with Aluminum (Al) applied onto the trimetal and photoresist appliedonto the Aluminum (Al). A mask is also illustrated.

FIG. 16A is a schematic illustration of another SiC wafer portion withthe trimetal, Al, photoresist and mask. The SiC wafer portion of FIG.16A illustrates by way of example one possible configuration for anaccelerometer.

FIG. 17 is a schematic illustration similar to FIG. 16 except that theimidized photo resist has been stripped away by the developer.

FIG. 18 is a schematic illustration similar to FIG. 17 which shows theresult of aqueous TMAH etching of the Al which was not protected by thephotoresist.

FIG. 19 is a schematic illustration similar to FIG. 18 which shows theremoval of the unimidized photoresist by use of Acetone.

FIG. 20 is a schematic illustration similar to FIG. 19 illustratingArgon plasma etching of the trimetal ohmic material with the Al as theetch mask.

FIG. 21 is a schematic illustration similar to FIG. 20 illustrating theapplication of photoresist and a mask.

FIG. 22 is a schematic illustration similar to FIG. 21 with theV-exposed photoresist developed and stripped away.

FIG. 23 is a schematic illustration similar to FIG. 22 with a layer ofIndium Tin Oxide, (ITO), deposited on the Al, oxide and undevelopedphotoresist.

FIG. 24 is a schematic illustration similar to FIG. 23 with the IndiumTin Oxide cap above the unexposed photoresist and the unexposedphotoresist removed.

FIG. 25 is a schematic illustration similar to FIG. 24 illustrating abore through the SiC wafer portion. FIG. 25 further illustratesselective deep reactive ion etching.

FIG. 26 is a schematic illustration similar to FIG. 25 illustrating theremoval of the Indium Tin Oxide and the Al etch mask by selectivechemistry that avoids destruction of the ohmic contact trimetal.

FIG. 27 is a schematic representation of a portion of a wafer similar tothat in FIG. 16A with the imidized photoresist stripped away by thedeveloper. The step in FIG. 27 is similar to the step illustrated inFIG. 17 except the structures of the wafers are different.

FIG. 28 is a schematic representation of the wafer portion of FIG. 27with unwanted Al etched away (removed) with aqueous TMAH. The step inFIG. 28 is similar to the step in FIG. 18 except the structures of thewafers are different.

FIG. 29 is a schematic representation of the unimidized photoresisthaving been removed by Acetone. The step illustrated in FIG. 29 issimilar to the step illustrated in FIG. 19 except the structures of thewafers are different.

FIG. 30 is a schematic representation of the etching of the trimetal inareas not covered with Al by Argon. The step illustrated in FIG. 30 issimilar to the step illustrated in FIG. 20 except that the structures ofthe wafers are different.

FIG. 31 is a schematic representation of the application of thephotoresist to the oxide. Imidized photoresist is stripped away by thedeveloper. The step illustrated in FIG. 31 is similar to the stepillustrated in FIG. 21 except the structures of the wafers aredifferent.

FIG. 32 is a schematic representation of the application of Indium TinOxide to the wafer portion illustrated in FIG. 31.

FIG. 33 is an enlargement of a portion of the wafer as illustrated inFIG. 32 showing the ITO partially covering the unimidized photoresistwhich resides in a defined cavity.

FIG. 34 is a schematic representation of the dry reactive ion etchingsimilar to FIG. 24 except the structures of the wafers are different.FIG. 34 illustrates the oxide exposed to the deep reactive ion etching.

FIG. 35 is a schematic illustration similar to FIG. 34 with two boresthrough the wafer illustrated.

FIG. 36 is a schematic of a completed accelerometer with the ITO and Alhaving been selectively stripped in a bath of hot phosphoric acidwithout attacking the ohmic contact.

FIGS. 37-42A illustrate schematically the preparation of the n-typeepilayer for metallization wherein:

FIG. 37 illustrates the application of photoresist, a desired mask andultraviolet light to a portion of a wafer.

FIG. 38 illustrates the application of Indium Tin Oxide or Nickel to theportion of the wafer as illustrated in FIG. 37.

FIG. 38A illustrates the portion of the wafer as illustrated in FIG. 38with Acetone having dissolved unimidized photoresist and lifted off theITO in certain places.

FIG. 39 illustrates etching of the n-type epilayer to form theresistors.

FIG. 40 illustrates the removal of the ITO/Nickel illustrated in FIG. 39which remained on the n-type piezoresistors.

FIG. 41 is identical to FIG. 40 except a recess has been manufactured inthe back side of the substrate.

FIG. 41A is similar to FIG. 41 except a different recess has beenmanufacture in the back side of the substrate and a different pattern orpiezoresistors has been formed out of the n-type epilayer.

FIGS. 42 and 42A are similar to FIGS. 41 and 41A respectively except anadditional layer of oxide has been grown or deposited over the n-typepiezoresistors and the substrate.

FIGS. 43 and 43A are similar to FIGS. 42 and 42A respectively withsections of the piezoresistors exposed by applying photoresist, bakingthe photoresist, applying the desired mask, exposing the desired portionof the photoresist to ultraviolet light to imidized the photoresist,develop and then wet etching the oxide in buffered hydrofluoric acid toexpose sections of the piezoresistors. Acetone is used to remove theunimidized photoresist.

FIGS. 44 and 44A illustrate application of the trimetal to thepiezoresistors and the application of Aluminum to the trimetal.

FIGS. 45 and 45A are similar to FIGS. 44 and 44A except the portions ofthe Aluminum and trimetal have been removed. Photoresist was applied,baked, masked and exposed to ultraviolet light as illustrated in FIG.16. Imidized photoresist was developed and stripped away as illustratedin FIG. 17, the Aluminum was etched away with TMAH as illustrated inFIG. 18. Next, the photoresist was striped away as illustrated in FIG.19 and then the trimetal was plasma etched as illustrated in FIG. 20.

FIG. 46 is similar to FIG. 45 except ITO has been applied to the waferportion. Before application of the ITO, photoresist was applied inpreparation for liftoff of ITO (or Nickel). The wafer portion of FIG. 46undergoes the same process as the wafer portion of FIG. 46A.

FIG. 46A is similar to FIG. 44A except photoresist is applied to thewafer, soft baked, masked and exposed to ultraviolet light asillustrated in FIGS. 21 and 22. Imidized photoresist is stripped awayand ITO is applied to the wafer. Acetone dissolves the unimidizedphotoresist and the ITO cap lifts off as illustrated in FIGS. 23 and 33.

FIGS. 47 and 47A illustrate deep reactive ion etching in the portions ofthe wafer with exposed oxide forming through holes in FIG. 47A. FIG. 47is not affected by the DRIE because of the ITO (or Nickel) coat.

FIGS. 48 and 48A illustrate the removal of the Aluminum and the ITO byselective etching to recover the clean surface of the trimetal whichpreferably is the Platinum layer of the trimetal.

A better understanding of the invention will be had when reference ismade to the following DESCRIPTION OF THE INVENTION and CLAIMS.

DESCRIPTION OF THE INVENTION

FIG. 1 is a prior art schematic illustration of a portion 100 of a wafer800 with ultraviolet light 107 applied to a mask 101 which is positionedin proximity to photoresist 106 applied to the back side 112 of a3C-SiC, 4H-SiC or 6H-SiC wafer 800. The front side 113 of the portion100 of a wafer 800 has an n-type epilayer 105 on the front side 113thereof. Reference numeral 113 indicates the p-n junction between then-type SiC epilayer and the p-type SiC substrate. FIG. 8 is an enlargedview of an entire SiC wafer 800 schematically illustrating a grid systemof approximately 500 areas where approximately 500 sensors, for example,can be manufactured.

Mask 101 can contact photoresist 106 or it can be in proximity to thephotoresist 106. Mask 101 includes transparent portions 103 and 108 aswell as a circular opaque portion 102. The SiC substrate 104 and then-type SiC epilayer 105 may be any of the 3C-SiC, 4H-SiC or 6H-SiCpolytypes. Ultraviolet light imidizes portions 110 and 111 of thephotoresist 106. Opaque portion 102 of mask 101 blocks, or masks,ultraviolet light from reaching the photoresist beneath it and thereforethat portion of the photoresist 106 is referred to as unimidized 109photoresist. Imidized portions 110, 111 of the photoresist 106 arestripped away with a chemical developer. Photoresists are photosensitivematerials which after photoimaging and subsequent processing, resistaction of certain chemicals in desired areas.

FIG. 2 is a prior art schematic illustration 200 of the portion 100 ofthe wafer 800 illustrated in FIG. 1 with the imidized photoresist 110,111 removed and with a layer of Indium Tin Oxide 201, deposited on thep-type SiC 104 portion of the back side 112 of the wafer 800. The IndiumTin Oxide (ITO) 201 does not completely cover the unimidized photoresist109 leaving an exposed portion 202 of unimidized photoresist. Acetone isused to dissolve the unimidized photoresist 109 and liftoff portion(cap)203 of the ITO 201 atop the unimidized photoresist 109.

FIG. 3 is a prior art schematic illustration 300 of the photoresist 109illustrated in FIG. 2 removed by bathing the wafer in Acetone, so as tolift off the ITO cap 203. Reference numeral 301 generally indicates thearea in which the unimidized photoresist 109 was removed.

FIG. 4 is a prior art schematic illustration 400 of deep reactive ionetching using Sulfur HexaFluorine (SF₆) to etch the back side 112 of theportion of the SiC wafer 800 forming a cavity 403. The shape of etchedcavity 403 can be shaped as dictated by the specifications for aparticular SiC sensor.

FIG. 5 is a prior art schematic illustration 500 without the ITO 201.ITO is removed from the SiC by submersing the wafer 800 in aHydrochloric Acid (HCI) bath. FIG. 6 is a prior art schematicillustration 600 of a pressure sensor formed in the SiC which has acavity 403 and n-type SiC piezoresistors 601, 602 and 603. FIG. 6A is aprior art schematic illustration 604 of the pressure sensor illustratedin FIG. 6 shown with pressure illustrated by arrow 605 applied thereto.FIG. 7 is a front side view 700 of the pressure sensor of FIGS. 6 and 6Aillustrating the piezoresistors 601, 602 and 603 as well as the cavity403 in phantom.

FIG. 8 is an enlarged view of an entire SiC wafer 800 schematicallyillustrating a grid system of approximately 500 areas whereapproximately, for example, 500 sensors can be manufactured. A differentnumber of sensors or devices may be manufactured. Reference numeral 801illustrates a grid or space where an accelerometer, for instance, may bemade. Reference numeral 802 illustrates a grid or space where a pressuresensor, for example, may be made. And, reference numeral 803 illustratesa grid or space where another accelerometer may be made. Devices havingarchitecture of all types may be made anywhere on the wafer using theprocesses disclosed herein. The processes disclosed herein enable themanufacture of SiC devices having three dimensional recesses.

FIGS. 9-13 illustrate one method of preparation of the n-type epilayerfor metallization. FIGS. 37-42 illustrate an example of a more specificmethod of preparation of the n-type epilayer for metallization. FIG. 9is a schematic illustration 900 of the application of oxide 901 on then-type SiC epilayer followed by application of photoresist 902 onto theoxide which is then followed by the application of mask 908 andultraviolet light 906. Mask 908 is illustrated spaced apart from thelayer of phortoresist 902. Alternately, the mask 908 could engage thephotoresist 902. Mask 908 is illustrated having opaque portions 903, 909and 910 and transparent portions 904 and 905. Ultraviolet light 906imidizes portions 907 of the photoresist.

Those skilled in the art will readily recognize that the illustrationsin all of the drawing Figures are not to scale. Typically, the p-typeSiC wafer is on the order of 400 microns thick, however, other widelyvarying thicknesses may be used without departing from the spirit andscope of the invention as claimed herein below. The wafer is held downon the chuck by suction. Photoresist is applied to the center of thewafer while it is being rotated at a speed of 1000 to 7000 revolutionsper minute and applied to thicknesses on the order of 6 microns. Otherthicknesses of photoresist may be used. The n-type SiC epilayer isapproximately 2 microns thick, however, the n-type epilayer can havethicknesses ranging from 0.5-5 microns thick. Contact metallization ispreferably sputter deposited to a thickness of 300 to 600 nm for thethree layer metal of Titanium, Tantalum Disilicide and Platinum.However, other thicknesses of the contact metal and other metals may beused.

The thickness of the oxide applied to the SiC (both the p-type and then-type epilayer) is in the range of 50 to 100 nm. Other thickness of theoxide are contemplated. The protective Aluminum is applied by anelectron beam evaporation (EBE) to a thickness of 1 to 2 microns but,again, other thickness or other deposition methods are contemplated. Theprotective Indium Tin Oxide or Nickel is sputter deposited to athickness in the range of 2 to 10 microns with other thicknessesspecifically contemplated within the scope of the claims.

FIG. 10 is a schematic illustration 1000 similar to FIG. 9 with theimidized photoresist 907 having been removed by developer and not shown.Reference numerals 1001 and 1002 illustrate areas where the imidizedphotoresist was removed.

FIG. 11 is a schematic illustration 1100 similar to FIG. 10 with theoxide 901 being etched with buffered hydrofluoric acid (BHF). Arrow 1103indicates wet etching of the oxide. Unimidized photoresist 902 protectsthe remainder of the oxide which is not etched. BHF etching continuesuntil such time as the oxide is completely etched away. FIG. 12 is aschematic illustration 1200 similar to FIG. 11 after etching of oxide901. Reference numerals 1201 and 1202 indicate the results of the BHFetching illustrated in FIG. 11.

FIG. 13 is a schematic illustration 1300 similar to FIG. 12 aftersubmersion of the wafer in Acetone which removed the unimidizedphotoresist 902 illustrated in FIG. 12.

FIG. 14 is a schematic illustration 1400 of a portion of a SiC waferwith layers Titanium 1501(shown in FIG. 15), Tantalum Disilicide 1502(shown in FIG. 15) and Platinum 1503 (shown in FIG. 15) (Ti/TaSi₂/Pt)(referred to herein as trimetal 1401 contact) applied to the oxide andto the n-type SiC epilayer. FIG. 14 represents the step of applying thecontact metallization prior to the formation of any three dimensionalrecesses (including apertures) in the SiC wafer. Applying the contactmetallization first enables photoresist to be spun on a substantiallyplanar surface at thicknesses of approximately 6 microns. Further,application of the contact metallization first allows the Aluminum to beeffectively applied at a thickness of 300 to 600 nm and allows the ITOto be effectively applied at a thickness of 2 to 10 microns. If thephotoresist is spun onto a wafer having recesses or three dimensionalapertures, then it will not be spread evenly with voids and beadsoccurring in the vicinity of the apertures resulting in low yield. Theinstant invention greatly increases the yield by etching the aperturesafter metallization occurs.

FIG. 15 is an enlargement of a portion of FIG. 14 illustrating thetrimetal 1401. Wires are eventually connected to the trimetal pads whenthe sensors are complete. Metals other than the trimetal may be used.The Titanium layer is preferably 100 nm thick, Tantalum Disilicide is400 nm thick and the top Platinum layer is 200 nm thick.

FIG. 16 is a schematic illustration 1600 of the SiC wafer portion ofFIG. 14 with Aluminum (Al) 1601 applied onto the trimetal 1401 andphotoresist 1602 spun onto the Aluminum (Al) 1601. Mask 1611 is alsoillustrated and contains opaque portions 1603 and a transparent portion1604. The mask 1602 can be spaced apart or it can be in contact with thephotoresist. Ultraviolet light imidizes portion 1605 of the photoresist1602. Unimidized portions 1612 of photoresist 1602 do not receiveultraviolet light. The steps illustrated in FIG. 16 and in FIG. 16A leadto the definition of areas in the wafer portions which will haverecesses or three dimensional structures.

FIG. 16A is a schematic illustration 1600A of another SiC wafer portionwith the trimetal 1401, Al 1601, photoresist 1602 and mask 1607 appliedthereto. The SiC wafer portion of FIG. 16A illustrates, by way ofexample, one possible configuration for an accelerometer. Mask 1607includes opaque portions 1608 and clear portions 1610. The mask may bein contact with the photoresist or it may be spaced apart as shown inFIG. 16A. Ultraviolet light imidizes portions of the photoresist 1602.The imidized portions 1609 of the photoresist in FIG. 16 A are strippedaway by developer. FIGS. 27-36 represent steps which follow theprocessing of the wafer portion 1600A illustrated in FIG. 16A.

FIGS. 17-26 represent the processing of the wafer portion 1600illustrated in FIG. 16. Those skilled in the art will readily recognizefrom reading this disclosure that the steps illustrated and taught inFIGS. 9-16, inclusive may be used to create virtually any pattern ofmetallic contact which engages the n-type epilayer. Further, thoseskilled in the art will readily recognize that the steps illustrated andtaught in FIGS. 9-16, inclusive, in combination with the stepsillustrated and taught in FIGS. 17-26 (described herein) and FIGS. 27-36(described herein), may be used to create any desired pattern ofmetallic contact which engages the n-type SiC epilayer in combinationwith any desired three dimensional structure. FIGS. 17-26 schematicallyillustrate the creation of an aperture which extends through the SiCwafer. Further, FIGS. 27-36 schematically the creation of a suspendedmass in a SiC wafer for use as an accelerometer. Application of themetallization to the n-type SiC at desired areas before etching intoand/or through the front the n-type SiC epilayer 105 and/or the p-typesubstrate 104 enables the bulk manufacture of multistructural,multifunctional devices out of a single SiC wafer 800. The areas whichare unnumbered in FIG. 8 will each contain a device which may be asensor. Those devices on the wafer 800 may all be the same or they maybe a mixture of many different devices. This gives industry the abilityto commercialize SiC as the semiconductor of choice because at any givenpoint in time there may not be a need for just one type of devicewhether it be a sensor or some other type of device.

FIG. 17 is a schematic illustration 1700 similar to FIG. 16 except thatthe imidized photoresist 1605 illustrated in FIG. 16 has been strippedaway by the developer. Next, FIG. 18 is a schematic illustration 1800similar to FIG. 17 which shows the result of aqueous TMAH etching of theAl 1601 which was not protected by the photoresist 1602. Referencenumeral 1801 illustrates a sharp corner located at the junction of theAl 1601 and the trimetal 1401 which is achieved by the anisotropicetching of the Al 1601. The anisotropic etching is performed byimmersing the entire wafer 800 in TMAH.

FIG. 19 is a schematic illustration 1900 similar to FIG. 18 which showsthe wafer portion 1900 after the removal of the unimidized photoresist1602. Acetone is used to remove the unimidized photoresist. Referencenumeral 1901 indicates the surface of the exposed trimetal 1401.

FIG. 20 is a schematic illustration similar to FIG. 19 illustratingArgon plasma etching 2003 of the trimetal 1401 ohmic material. Otherinert gasses may be used to etch the trimetal which is approximately 300to 600 nm thick. Reference numeral 2003 indicates the direction of theargon plasma etching.

FIG. 21 is a schematic illustration 2100 similar to FIG. 20 illustratingthe application of photoresist 2104 and a mask 2105 to the waferportion. A portion of the trimetal has been removed and that portion nowis covered with photoresist 2104. Photoresist 2104 is spun onto thewafer which is at this point in the process substantially planar. Thetrimetal is only 300 to 600 nm thick, the Al is 1-2 microns thick, andthe photoresist is approximately 6 microns thick. FIG. 21 is a schematicillustration which presents an exaggerated three dimensional appearanceof the trimetal 1401, Al 1601 and photoresist 2104. Mask 2105 includesan opaque portion 2101 and clear portions 2103. Mask 2105 is spacedapart for illustration but in reality it may touch the photoresist inplaces. Ultraviolet light 2102 is applied to the mask imidizing aportion of the photoresist 2104 under the transprent portions 2103 ofthe mask. The imidized photoresist is then stripped away with developerwith the unimidized photoresist 2104 remaining as illustrated in FIG.22. FIG. 22 is a schematic illustration 2200 similar to FIG. 21 with theimidized photoresist developed and stripped away.

FIG. 23 is a schematic illustration 2300 similar to FIG. 22 with a layerof Indium Tin Oxide, (ITO) 2301, deposited on the Al 1601, oxide 901 andwhich partially covers undeveloped photoresist 2104. Since theunimidized photoresist 2104 is approximately 6 microns thick and the ITO(or Nickel) is only 1-2 microns thick, a portion of the vertical rise2302 and 2303 of the unimidized photoresist 2104 will be exposed and notcovered by the ITO. In effect, an ITO (or Nickel) cap 2301 is formed ontop of the unimidized photoresist (2104). The ITO cap 2301 is strippedaway when the wafer is immersed in Acetone because the Acetone dissolvesthe unimidized photoresist 2104.

FIG. 24 is a schematic illustration 2400 similar to FIG. 23 with theIndium Tin Oxide Cap above the undeveloped photoresist and theundeveloped photoresist removed. FIG. 24 further illustrates selectivedeep reactive ion etching. Arrow 2401 indicates the direction of theetching of the SiC by the SF₆ in the dry reactive ion etching process(DRIE) which may be timed thus controlling the depth of the etching. Inthe example of FIG. 24, the DRIE continues under the influence of anelectric field until the wafer has been completely pierced asillustrated in FIG. 25. FIG. 25 is a schematic illustration 2500 similarto FIG. 24 illustrating a bore 2501 through the SiC wafer portion. InFIG. 25 the wafer still has the Al 1601 and the ITO (or Nickel) 2301coverings. Hot phosphoric acid is used to remove the protective ITO andAl coverings. FIG. 26 is a schematic illustration 2600 similar to FIG.25 illustrating the removal of the Indium Tin Oxide and the Al and acompleted wafer portion. The description above explains selectivechemical removal.

FIG. 27 is a schematic representation 2700 of a portion of a wafersimilar to that in FIG. 16A with the imidized photoresist 1609 (FIG.16A) stripped away by the developer. The step in FIG. 27 is similar tothe step illustrated in FIG. 17 except the structures of the wafers aredifferent and the metallization patterning for engagement with then-type is different. FIGS. 16A and FIG. 27 illustrate cavities 403etched into the backside of the wafer portion.

FIG. 28 is a schematic representation 2800 of the wafer portion of FIG.27 with unwanted Al 1601 etched away (removed) with aqueous TMAH inthose areas unprotected by unimidized photoresist. The step in FIG. 28is similar to the step in FIG. 18 except the structures of the wafersare different and the metallization patterning for engagement with then-type SiC epilayer is different.

FIG. 29 is a schematic illustration 2900 of the unimidized photoresist1602 illustrated in FIG. 28 having been removed by Acetone. The stepillustrated in FIG. 29 is similar to the step illustrated in FIG. 19except the structures of the wafers are different and the metallizationpatterning for engagement with the n-type SiC epilayer is different.

FIG. 30 is a schematic illustration 3000 of Argon plasma etching 3003 ofthe trimetal 1401 in areas not covered with Al 1601. The stepillustrated in FIG. 30 is similar to the step illustrated in FIG. 20except that the structures of the wafers are different and themetallization patterning for engagement with the n-type SiC epilayer isdifferent. An electric field enables etching with the inert Argon plasmaOther inert gasses may be used.

FIG. 31 is a schematic illustration 3100 of the application of thephotoresist 3101 to the oxide 901. Mask 3102 includes opaque portions3108 and transparent portions 3103, 3104 and 3105. Ultraviolet light3106 imidizes those portions of photoresist under the transparentportions 3103, 3104 and 3105 of the mask. Imidized photoresist isstripped away by the developer. Again, FIG. 31 is an illustration and isnot to scale. The surface defined by the the oxide 901 and Al 1601 ontop of the contact metallization 1401 is substantially planar becausethe oxide 901 is 50-100 nm thick, the trimetal 1401 is 300 to 600 nmthick, and the Al 1601 is only 1-2 microns thick. The photoresist isspun onto the wafer 800 such that it has a thickness of approximately 6microns thick. Since photoresist is applied 6 microns thick, the heightabove the n-type SiC epilayer varies between a minimum of 50 nm which isthe minimum thickness of the oxide 901 to a maximum of 600 nm (maximumthickness of the trimetal) plus the thickness of Al 1601 at its maximumof 2 microns. Therefore, the profile of the surface of the materialsatop the wafer illustrated in FIG. 31 varies from a minimum of 50 nm(minimum oxide thickness) to a maximum of 2,600 nm (600 nm (maximumtrimetal 1401 thickness) plus 2,000 nm (maximum thickness of Al 1601)).Since 6 microns is equal to 6,000 nm coverage of the wafer is good andyield of the SiC wafer is very high. The step illustrated in FIG. 31 issimilar to the step illustrated in FIG. 21 except the structures of thewafers are different and the contact metallization patterning forengagement with the n-type SiC epilayer is different

FIG. 32 is a schematic illustration of the application of a layer IndiumTin Oxide 3201 or Nickel at a thickness of 1-2 microns to the waferportion illustrated in FIG. 31 after the imidized photoresist has beenstripped away. The results of the application of ITO in FIG. 32 are verysimilar to the application of ITO or Nickel as in FIG. 23 previouslydescribed above. The ITO 3201, due to its relatively thin thickness, ascompared to that of the unimidized photoresist 3101 underlying a portionof the ITO, does not completely cover the unimidized photoresist 3301 asis best viewed in FIG. 33. FIG. 33 is an enlargement of a portion of thewafer as illustrated in FIG. 32 showing the ITO 3201 partially coveringthe unimidized photoresist 3101. Reference numerals 3301 and 3302indicate exposed areas of unimidized photoresist which are subsequentlyattacked and dissolved by Acetone leaving the structure illustrated inFIG. 34. Deep reactive ion etching using an inert gas plasma isindicated by flow arrow 3403 in FIG. 34. FIG. 34 is a schematicillustration 3400 of the dry reactive ion etching 3403 similar to FIG.24 except the structures of the wafers are different and the contactmetallization pattern is different FIG. 34 illustrates the oxide 901exposed to the deep reactive ion etching with a gas, for example, Ar orunder the influence of an electric field.

FIG. 35 is a schematic illustration 3500 similar to FIG. 34 with twobores 3501 and 3502 through the wafer portion illustrated. Indium TinOxide 3201 and Al 1601 are illustrated in FIG. 35 and they are removedby immersing the wafer portion in hot phosphoric acid. FIG. 36 is aschematic illustration 3600 of a completed accelerometer with the ITOand Al having been removed in a bath of hot phosphoric acid. A bridgenot shown in this view suspends the proof mass 3503 illustrated in FIGS.35 and 36.

FIGS. 37-42 illustrate schematically the preparation of the n-typeepilayer for metallization. FIG. 37 is a view 3700 which illustrates theapplication of photoresist 3702, a desired mask 3708 with transparentportions 3704, 3705, and 3705A and ultraviolet light 3706 to a portionof a wafer 3700. Imidized portions 3707 of photoresist 3702 are strippedaway by developer.

FIG. 38 is a view 3800 which illustrates the application of Indium TinOxide or Nickel to a 3801 to the portion of the wafer as illustrated inFIG. 37. Reference numerals 3802 indicate areas not covered by the ITO.FIG. 38A is a view 3800A which illustrates the portion of the wafer asillustrated in FIG. 38 with Acetone having dissolved unimidizedphotoresist 3702 resulting in the lift off of ITO 3801 in certaindesired places leaving n-type epilayer 105 covered with ITO 3801. Plasmaetching of the n-type epilayer forms piezoresistors as shown in FIG. 39.FIG. 40 is a view 4000 which illustrates the removal of the ITO/Nickelillustrated in FIG. 39 which remained on the n-type piezoresistors.

FIG. 41 is a view 4100 which is identical to FIG. 40 except a recess 403has been manufactured in the back side of the substrate. FIG. 41A is aview 4100A similar to FIG. 41 except a different recess 4103A has beenmanufactured in the back side of the substrate 4100A and a differentpattern of piezoresistors has been formed out of the n-type epilayer.

FIGS. 42 and 42A illustrate views 4200, 4200A which are similar to FIGS.41 and 41A respectively except an additional layer of oxide 4201 hasbeen grown or deposited over the n-type piezoresistors 105 and thesubstrate.

FIGS. 43 et seq. represent a side by side comparison of a pressuresensor (FIGS. 43-48) with an accelerometer (FIGS. 43A-48A). Variousaspects of the steps shown in these drawing figures has been shown inFIGS. 13 to FIGS. 36 above. Reference should be made to FIGS. 13 to 36and to the description of those drawing figures to better aid in anunderstanding of FIGS. 43 et seq. Those skilled in the art will readilyrecognize that many different configurations of piezoresistors may beemployed on a multitude of different substrates without departing fromthe spirit and scope of the appended claims.

FIGS. 43 and 43A illustrate views 4300, 4300A which are similar to FIGS.42 and 42A, respectively, with the piezoresistors exposed by applyingphotoresist, balking the photoresist, applying the desired mask,exposing the desired portion of the photoresist to ultraviolet light toimidized the photoresist and then wet etching the oxide 4201 in bufferedhydrofluoric acid to expose portions of the piezoresistors where metalcontacts will be deposited. Acetone is used to remove the unimidizedphotoresist. FIGS. 43 and 43A illustrate the piezoresistors exposed formetallization.

FIGS. 44 and 44A illustrate views 4400, 4400A which schematicallyindicate application of the trimetal 4401 to the piezoresistors 105 andthe application of Aluminum 4402 to the trimetal 4401.

FIGS. 45 and 45A are views 4500, 4500A which are similar to FIGS. 44 and44A except portions of the Aluminum 4402 and trimetal 4401 have beenremoved. Photoresist was applied, baked, masked and exposed toultraviolet light as illustrated in FIG. 16. Imidized photoresist wasdeveloped and stripped away as illustrated in FIG. 17, and the Aluminumwas etched away with TMAH as illustrated in FIG. 18. Next, thephotoresist was stripped away as illustrated in FIG. 19 and then thetrimetal 4401 was plasma etched as illustrated in FIG. 20. FIGS. 45 and45A illustrate oxide exposed.

FIG. 46 is a view 4600 similar to FIG. 45 except ITO 4601 has beenapplied to the wafer portion. The wafer portion of FIG. 46 undergoes thesame process as the wafer portion of FIG. 46A.

FIG. 46A is a view 4600A similar to FIG. 45A except photoresist isapplied to the wafer, soft baked, masked and exposed to ultravioletlight as illustrated in FIGS. 21 and 22. Imidized photoresist isstripped away and ITO 4601 is applied to the wafer. Acetone dissolvesthe unimidized photoresist and carries away with it ITO caps residingabove the unimidized photoresist as best illustrated in FIGS. 23 and 33.Reference numeral 4602 as indicated in FIG. 46A indicates exposed oxidewhich is ready for deep reactive ion etching. Those exposed sections areexposed because the photoresist and ITO has been stripped away.

FIGS. 47 and 47A illustrate views 4700, 4700A, respectively, of deepreactive ion etching in the portions of the wafer with exposed oxide4201 forming through holes 4701 in FIG. 47A. No through hole is formedin FIG. 47 which remains as a diaphragm for a pressure sensing. Athrough hole is formed in FIG. 47A which makes it an accelerometer.FIGS. 48 and 48A illustrate views 4800, 4800A of the removal of theAluminum and the ITO to recover the clean surface of the trimetal 4401which preferably is the Platinum layer of the trimetal.

The invention has been described herein by way of example only. Thoseskilled in the art will readily recognize that structural changes,method changes and material changes may be made to those disclosedherein without departing from the spirit and scope of the appendedclaims.

I claim:
 1. A method of making a SiC accelerometer from a SiC wafer,said SiC wafer comprising p-type SiC substrate and an n-type SiCepilayer, comprising the steps of: applying a layer of oxide on saidn-type epilayer of said SiC; applying a first layer of photoresist onsaid layer of oxide; masking said first layer of photoresist withultraviolet light imidizing a portion of said first layer of photoresistand stripping away said imidized photoresist with developer and leavingunimidized photoresist on said layer of oxide; dry etching exposedoxide; removing the unimidized first layer of photoresist; depositingcontact metallization; depositing Aluminum on said contactmetallization; applying a second layer of photoresist on said Aluminum;masking said second layer of photoresist with ultraviolet lightimidizing a portion of said second layer of photoresist and strippingaway said imidized portion of said second layer of photoresist withdeveloper and leaving behind unimidized photoresist; etching Aluminumnot covered by unimidized photoresist; removing unimidized photoresist;dry etching said contact metallization not covered by Aluminum; applyinga third layer of photoresist to said Aluminum and said oxide and maskingsaid third layer of photoresist imidizing a portion of said photoresistand stripping away said imidized portion of said photoresist leavingbehind unimidized photoresist; applying a masking layer selected fromthe group consisting of Indium Tin Oxide and Nickel over said Aluminum,said oxide and said unimidized photoresist leaving a portion of saidunimidized photoresist exposed; removing said unimidized portion of saidthird layer of photoresist together with said a portion of said maskinglayer selected from the group of Indium Tin Oxide and Nickel whichcovers said unimidized photoresist; and, dry etching portions of saidoxide, said n-type epilayer of said SiC substrate and said p-type SiCsubstrate which are not protected by said masking layer selected fromthe group consisting of Indium Tin Oxide and Nickel; and, dissolvingsaid Aluminum and said masking layer.
 2. A method of making a SiCaccelerometer as claimed in claim 1 wherein said step of dry etchingportions of said oxide, said n-type epilayer of said SiC substrate andsaid p-type SiC substrate which are not protected by said making layerforms an aperture in said wafer.
 3. A SiC accelerometer produced by theprocess of claim
 1. 4. A method of making a SiC accelerometer from a SiCwafer, said SiC wafer comprising p-type SiC and an n-type epilayer,comprising the steps of: depositing contact metal on said n-type layer;protecting a portion of said contact metal leaving a remainder of saidcontact metal unprotected; etching said remainder of said contact metal;and, etching said n-type SiC epilayer and said p-type SiC.
 5. A methodof making a SiC accelerometer as claimed in claim 4 wherein said contactmetal is comprised of Titanium, Tantalum Silicate and Platinum.
 6. Amethod of making a SiC accelerometer as claimed in claim 4 wherein saidstep of etching said n-type SiC epilayer and said p-type SiC isperformed by deep reactive ion etching.
 7. A method of making a SiCaccelerometer as claimed in claim 4 wherein said step of etching saidn-type SiC epilayer and said p-type SiC forms an aperture therein.
 8. Amethod of making a SiC accelerometer as claimed in claim 4 wherein saidstep of etching said n-type SiC epilayer and said p-type SiC forms arecess therein.
 9. A method of making a sensor from a SiC wafer, saidSiC wafer comprising p-type SiC and an n-type epilayer, comprising thesteps of: depositing contact metal on said n-type layer; protecting aportion of said contact metal by covering it with a protective metalleaving a remainder of said contact metal unprotected and uncovered;etching said remainder of said contact metal; and, removing saidprotective metal from said contact metal.
 10. A method of making asensor as claimed in claim 9 wherein said contact metal comprises:Titanium contacting said n-type SiC epilayer, Tantalum Disilicidecontacting said Titanium and Platinum contacting said TantalumDisilicide.
 11. A method of making a sensor as claimed in claim 9wherein said step of etching said remainder of said contact metal isdone with a plasma of inert gas.
 12. A method of making a sensor asclaimed in claim 11 where said inert gas is Argon.
 13. A method ofmaking a sensor as claimed in claim 9 wherein said protective metal isAluminum.
 14. A method of making a sensor as claimed in claim 9 whereinthe step of removing said protective metal from said contact metal isperformed with hot phosphoric acid.
 15. A method of making a sensor asclaimed in claim 9 further comprising the step of: etching said p-typeSiC from the side opposite said n-type epilayer.
 16. A SiC accelerometerproduced by the process of claim
 9. 17. A method of making a sensor froma SiC wafer, said SiC wafer comprising p-type SiC and an n-typeepilayer, comprising the steps of: depositing contact metal on saidn-type layer; protecting a portion of said contact metal by covering itwith a protective metal leaving a remainder of said contact metalunprotected and uncovered; etching said remainder of said contact metalexposing said n-type epilayer; applying a second layer of protectivematerial over said protective metal and said n-type epilayer; removing aportion of said second layer of protective material; and, etching, bydeep reactive ion etching, a three-dimensional recess into said n-typeand said p-type SiC.
 18. A method of making a sensor as claimed in claim17 wherein said step of etching said remainder of said contact metal isperformed with an inert gas plasma and where said step of etching athree-dimensional recess into said n-type epilayer and said p-type SiCforms an aperture in said SiC wafer.
 19. A method of making a sensor asclaimed in claim 18 wherein said aperture extends completely throughsaid SiC wafer.
 20. A method of making a sensor as claimed in claim 19wherein said aperture forms a proof mass useable as an accelerometer.21. A method of making a sensor as claimed in claim 17 wherein saidsecond protective layer is selected from the group consisting of IndiumTin Oxide and Nickel.
 22. A SiC accelerometer produced by the process ofclaim
 17. 23. A method of simultaneously manufacturing a plurality ofmultistructural, multifunctional sensors from a SiC wafer, said SiCwafer comprising p-type SiC and an n-type SiC epilayer, comprising thesteps of: depositing contact metal on said n-type layer; protecting aportion of said contact metal by covering it with a protective metalleaving a remainder of said contact metal unprotected and uncovered;etching said remainder of said contact metal exposing said n-typeepilayer; applying a second layer of protective material over saidprotective metal and said n-type epilayer; removing a portion of saidsecond layer of protective material from selected areas of said SiCwafer exposing said n-type epilayer; and, etching, by deep reactive ionetching, three-dimensional recesses in said exposed areas of said n-typeepilayer with said etching continuing into said p-type SiC.
 24. A methodas claimed in claim 23 wherein said step of depositing contact metal onsaid n-type layer includes depositing Titanium followed by depositing ofTantalum Silicide followed by Platinum.
 25. A method as claimed in claim23 wherein said step of protecting a portion of said contact metal bycovering it with a protective metal leaving a remainder of said contactmetal unprotected and uncovered is performed by depositing Aluminum asthe protective metal.
 26. A method as claimed in claim 23 wherein saidstep of etching said remainder of said contact metal exposing saidn-type epilayer is performed with an inert gas plasma.
 27. A method asclaimed in claim 23 wherein said step of applying a second layer ofprotective material over said protective metal and said n-type epilayeris performed by depositing a protective material selected from the groupof Indium Tin Oxide and Nickel.
 28. A method as claimed in claim 23wherein said step of removing a portion of said second layer ofprotective material from selected areas of said SiC wafer exposing saidn-type epilayer is performed by dissolving photoresist underlying saidsecond layer of protective material.
 29. A method as claimed in claim 28wherein said step of etching, by deep reactive ion etching,three-dimensional recesses in said exposed areas of said n-type epilayerwith said etching continuing into said p-type SiC forms apertures whichextend completely through said SiC wafer.
 30. A method as claimed inclaim 23 further comprising the step of: separating saidmultistructural, multifunctional sensors apart from each other.
 31. Amethod of simultaneously manufacturing a plurality of multistructural,multifunctional sensors from a SiC wafer, said SiC wafer comprisingp-type SiC and an n-type SiC epilayer, comprising the steps of:depositing Titanium metal on said n-type layer; depositing TantalumDisilicide on said Titanium metal; depositing Platinum on said TantalumDisilicide; protecting a portion of said metals by covering saidPlatinum with Aluminum leaving a remainder of said contact metalunprotected and uncovered; etching, with an inert gas plasma, saidremainder of said contact metal exposing said n-type epilayer; applyinga layer of Indium Tin Oxide over said Aluminum and said n-type epilayerto protect said Aluminum and said n-type epilayer; removing a portion ofsaid Indium Tin Oxide from selected areas of said SiC wafer exposing aportion of said n-type epilayer; and, etching, by deep reactive ionetching, three-dimensional recesses in said exposed portions of saidn-type epilayer with said etching continuing into said p-type SiC.
 32. Aplurality of multistructural and multifunctional SiC sensors produced bythe process of claim
 31. 33. A method as claimed in claim 31 furthercomprising the steps of: etching a portion of the side of the p-type SiCopposite of said n-type SiC.
 34. A plurality of multistructural andmultifunctional SiC sensors produced by the process of claim
 33. 35. Amethod as claimed in claim 31 wherein said etching, by deep reactive ionetching, forms a plurality of accelerometers.
 36. A method as claimed inclaim 30 further comprising the step of: separating saidmultistructural, multifunctional sensors apart from each other.
 37. Amethod of making a pressure sensor from a SiC wafer, said SiC wafercomprising p-type SiC and an n-type SiC epilayer, comprising the stepsof: depositing contact metal on said n-type layer; protecting a portionof said contact metal by covering it with a protective metal leaving aremainder of said contact metal unprotected and uncovered; etching saidremainder of said contact metal; removing said protective metal fromsaid contact metal; and, etching said p-type SiC opposite said n-typeSiC epilayer forming a cavity in said SiC wafer.
 38. A method ofsimultaneously manufacturing a plurality of multistructural,multifunctional sensors from a SiC wafer, said SiC wafer comprisingp-type SiC and an n-type SiC epilayer, comprising the steps of:depositing contact metal on said n-type SiC epilayer, protecting aportion of said contact metal by covering it with a protective metalleaving a remainder of said contact metal unprotected and uncovered;etching said remainder of said contact metal exposing a portion of saidn-type SiC epilayer; applying a second layer of protective material oversaid protective metal and said n-type epilayer; removing a portion ofsaid second layer of protective material from selected areas of said SiCwafer exposing a portion of said n-type SiC epilayer; etching,selectively, by deep reactive ion etching, three-dimensional recesses insaid exposed areas of said n-type SiC epilayer with said etchingcontinuing into said p-type SiC; and, etching, selectively, by deepreactive ion etching, three-dimensional recesses in said p-type SiC. 39.A method of simultaneously manufacturing a plurality of multistructural,multifunctional devices from a SiC wafer, said SiC wafer comprisingp-type SiC substrate and an n-type SiC epilayer, comprising the stepsof: depositing contact metal on said n-type layer; protecting a portionof said contact metal by covering it with a protective metal leaving aremainder of said contact metal unprotected and uncovered; etching saidremainder of said contact metal exposing said n-type epilayer; applyinga second layer of protective material over said protective metal andsaid n-type epilayer; removing a portion of said second layer ofprotective material from selected areas of said SiC wafer exposing saidn-type epilayer; and, etching, by deep reactive ion etching,three-dimensional recesses in said exposed areas of said n-type epilayerwith said etching continuing into said p-type SiC.
 40. A method asclaimed in claim 39 wherein said device is a sensor.
 41. A deviceproduced by the method of claim
 39. 42. A method of making a sensor froma SiC wafer, said SiC wafer comprising p-type SiC, comprising the stepsof: depositing contact metal on said p-type layer; protecting a portionof said contact metal by covering it with a protective metal leaving aremainder of said contact metal unprotected and uncovered; etching saidremainder of said contact metal; and, removing said protective metalfrom said contact metal.